1. Field of the Invention
The present invention relates to an image formation control apparatus, an image forming system, an image formation control method, and a storage medium storing an image formation control program, which are applied to printing by two connected image forming apparatuses.
2. Description of the Related Art
Conventionally, an image forming apparatus is controlled as follows to print images on both sides of a recording sheet. First, the recording sheet fed from a sheet feeding unit of the image forming apparatus is conveyed to an image forming unit, an image is formed on a first side (a front side) of the recording sheet, and the image is fixed by heat onto the recording sheet by a fixing unit. Then, the recording sheet is inverted by an inverting mechanism installed in a conveyance path, the inverted recording sheet is again conveyed to the image forming unit, an image is formed on a second side (a back side) of the recording sheet, and the image is fixed by heat onto the recording sheet.
When the images are printed on both the sides of the recording sheet according to the above-mentioned control, the recording sheet is circularly conveyed within the unit in general. Therefore, as shown in FIG. 13, when an image forming apparatus is used alone, productivity (the number of the recording sheets ejected per unit time) for double-sided print is half the productivity for one side print.
Thus, a connected image forming system, which connects two image forming apparatuses to perform a print operation, has been proposed to increase the productivity of the double-sided print with a simple method (for example, see Japanese Laid-Open Patent Publication (Kokai) No. 2006-58881 (JP 2006-58881A)). In the connected image forming system, a first image forming apparatus at the upstream side (a first stage) forms and fixes an image onto a first side of a recording sheet. Then, the recording sheet is inverted and is conveyed to a second image forming apparatus at the downstream side (a second stage). The second image forming apparatus forms and fixes an image onto a second side of the recording sheet, and ejects the sheet from the apparatus.
The connected image forming system increases the productivity, which is converted to the output number of recording sheets, for the double-sided print so as to be almost equal to the productivity for the one side print sheet, as shown in FIG. 13.
When the first image forming apparatus cannot continue to print, the connected image forming system is able to execute double-sided print only by the second image forming apparatus. When the first image forming apparatus cannot feed a recording sheet, when toner is empty, or when a waste toner container that collects used waste toner is full etc., the first image forming apparatus cannot continue printing.
However, since the conventional connected image forming system supplies electric power to the first image forming apparatus that cannot continue printing even when executing the double-sided print only by the second image forming apparatus, there was a problem of consuming energy vainly.